Apex domains cannot have CNAME records.
Question and response
Question
dig compute-1.amazonaws.com. NS
Answer
compute-1.amazonaws.com. 5 NS ns-479.awsdns-59.com.
compute-1.amazonaws.com. 5 NS ns-943.awsdns-53.net.
compute-1.amazonaws.com. 5 NS ns-1390.awsdns-45.org.
compute-1.amazonaws.com. 5 NS ns-1749.awsdns-26.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0